1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a field sequential liquid crystal display.
2. Description of the Related Art
A liquid crystal display is a device for applying an electric field to liquid crystal material having anisotropic dielectric which is injected between two substrates and for controlling intensity of the electric field to adjust an amount of light transmitting through the substrates from an external light source (backlight) to obtain a desired image signal.
This liquid crystal display is a typical device of easy-portable flat displays and among the flat displays a TFT-LCD using thin film transistor (TFT) as switching devices is mainly used.
The liquid crystal display, in general, displays a desired image by forming primary color filter layers having red (R), green (G), and blue (B) colors on one of the two substrates and by controlling the amount of light transmitting through the color filter layers. That is, the conventional color filter liquid crystal display displays a desired image by controlling the amount of light transmitting through the R, G and B color filter layers to combine R, G and B colors when the light projected from a single light source passes through the R, G and B color filters.
However, since the liquid crystal display for displaying an image using the single light source and the three color filter layers need unit pixels respectively corresponding to R, G and B regions, the conventional liquid crystal display needs pixels more than three times when displaying a black-white image. Therefore, in order to obtain a high definition image, a precise manufacturing technology is required of the liquid crystal display panel. In addition, such liquid crystal display had disadvantage in manufacturing of forming an additional color filter layer on a substrate and has a low brightness because of low light transmission of the color filter.
In order to overcome these drawbacks, a field sequential liquid crystal display is proposed.
The field sequential liquid crystal display turns on independent light sources of R, G and B colors sequentially and applies corresponding color signals to respective pixels in synchronizing with the turning-on period to obtain a full color image. According to the field sequential liquid crystal display, one pixel is not divided into unit pixels of R, G and B colors but R, G and B primary color light, which are output from R, G and B color backlights respectively, are sequentially displayed in time divisional way to display an image using an afterimage.
That is, the field sequential liquid crystal display does not have a color filter but includes a sequential backlight for emitting R, G and B color lights sequentially.
In addition, the field sequential liquid crystal display is generally driven by a digital method such that one field frame is time-divided into at least three sub-frames and red color light, green color light, and blue color light are sequentially displayed in the respective sub-frames to display colors.
At this time, each of the sub-frames is divided into a region of addressing respective liquid crystal cell arrays, a region of charging liquid crystal cells with an applied image signal, a region of projecting the backlight, and a region of resetting the liquid crystal cells. That is, each of the sub-frames can project a corresponding backlight only after an image signal is completely input to all liquid crystal cells (particularly, a liquid crystal cell finally addressed).
Due to this structural problem, the conventional field sequential liquid crystal display requires time for transmitting video data to all pixels in a state when one frame is divided into three sub-frames, and thus time for displaying actual brightness is restricted.
Therefore, the field sequential liquid crystal display must project light only after signals are addressed to the respective pixels and the liquid crystal is completely driven by the signals, and thus requires an additional liquid crystal cell structure and a driving method thereof in order to lengthen time for projecting light.